wabt.js is a port of WABT to the Web, allowing you to manipulate WebAssembly modules using a JavaScript API.

$> npm install wabt

require("wabt")().then(wabt => {
  var wasm = ...; // a buffer holding the contents of a wasm file

  var myModule = wabt.readWasm(wasm, { readDebugNames: true });
  myModule.applyNames();

  var wast = myModule.toText({ foldExprs: false, inlineExport: false });

  console.log(wast);
});

The buildbot also publishes nightly versions once a day if there have been changes. The latest nightly can be installed through

$> npm install --save-exact wabt@nightly

or you can use one of the previous versions instead if necessary. Note the --save-exact when using a nightly.

• From GitHub via jsDelivr:
  https://cdn.jsdelivr.net/gh/AssemblyScript/wabt.js@VERSION/index.js
• From npm via jsDelivr:
  https://cdn.jsdelivr.net/npm/wabt@VERSION/index.js
• From npm via UNPKG:
  https://unpkg.com/wabt@VERSION/index.js

Replace VERSION with a specific version or omit it (not recommended in production) to use master/latest.

• parseWat(filename: string, buffer: string | Uint8Array, options?: WasmFeatures): WasmModule
  Parses a WebAssembly text format source to a module.

• readWasm(buffer: Uint8Array, options: ReadWasmOptions & WasmFeatures): WasmModule
  Reads a WebAssembly binary to a module.

• WasmModule
  A class representing a WebAssembly module.

  • validate(): void
    Validates the module. Throws if not valid.
  • resolveNames(): void
    Resolves names to indexes.
  • generateNames(): void
    Generates textual names for function types, globals, labels etc.
  • applyNames(): void
    Applies textual names. Throws on error.
  • toText(options: ToTextOptions): string
    Converts the module to wat text format.
  • toBinary(options: ToBinaryOptions): ToBinaryResult
    Converts the module to a wasm binary.
  • destroy(): void
    Disposes the module and frees its resources.

• ReadWasmOptions
  Options modifying the behavior of readWasm.

  • readDebugNames: boolean
    Reads textual names from the name section.

• ToTextOptions
  Options modifying the behavior of WasmModule#toText.

  • foldExprs: boolean
  • inlineExport: boolean

• ToBinaryOptions
  Options modifying the behavior of WasmModule#toBinary.

  • log: boolean
  • canonicalize_lebs: boolean
  • relocatable: boolean
  • write_debug_names: boolean

• ToBinaryResult
  Result object of WasmModule#toBinary.

  • buffer: Uint8Array
    The wasm binary buffer.
  • log: string
    Generated log output.

• WasmFeatures
  Post-MVP WebAssembly features to legalize.

  • exceptions: boolean
    Exception handling (proposal).
  • mutable_globals: boolean
    Import/Export mutable globals (proposal).
  • sat_float_to_int: boolean
    Non-trapping Float-to-int Conversions (proposal).
  • sign_extension: boolean
    Sign-extension operators (proposal).
  • simd: boolean
    128-bit packed SIMD (proposal).
  • threads: boolean
    Threading (proposal).
  • multi_value: boolean
    Multi-value (proposal).
  • tail_call: boolean
    Tail Call (proposal).
  • bulk_memory: boolean
    Bulk Memory Operations and Conditional Segment Initialization (proposal).
  • reference_types: boolean
    Reference Types (proposal).
  • annotations: boolean
    Custom Annotation Syntax for the Wasm Text Format (proposal).
  • gc: boolean
    Garbage collection (proposal).

Node.js ports of the following command line tools are included in the package as well:

• wasm2c converts a WebAssembly binary file to a C source and header.
• wasm2wat translates from WebAssembly binary format to text format.
• wat2wasm translates from WebAssembly text format to binary format.
• wasm-decompile decompiles a wasm binary into readable C-like syntax.
• wasm-interp decodes and runs a WebAssembly binary file using a stack-based interpreter.
• wasm-objdump prints information about a wasm binary. Similiar to objdump.
• wasm-opcodecnt counts opcode usage for instructions.
• wasm-strip removes sections of a WebAssembly binary file.
• wasm-validate validates a file in WebAssembly binary format.

The tools can also be run ad hoc (without explicitly installing the package), for example with:

$> npx -p wabt wasm2wat myModule.wasm -o myModule.wat